Air flow rate

Until recently most industrial scale, and even bench scale, bioreactors of this type were agitated by a set of Rushton turbines having about one-thind the diameter of the bioreactor (43) (Fig. 3). In this system, the air enters into the lower agitator and is dispersed from the back of the impeller blades by gas-fiUed or ventilated cavities (44). The presence of these cavities causes the power drawn by the agitator, ie, the power requited to drive it through the broth, to fall and this has important consequences for the performance of the bioreactor with respect to aeration (35). k a has been related to the power per unit volume, P/ U, in W/m and to the superficial air velocity, in m/s (20), where is the air flow rate per cross-sectional area of bioreactor. This relationship in water is... 

An important characteristic of solvents is rate of evaporation. Rates of solvent loss are controUed by the vapor pressure of the solvent(s) and temperature, partial pressure of the solvent over the surface, and thus the air-flow rate over the surface, and the ratio of surface area to volume. Tables of relative evaporation rates, in which -butyl acetate is the standard, are widely used in selecting solvents. These relative rates are deterrnined experimentally by comparing the times required to evaporate 90% of a weighed amount of solvent from filter paper under standard conditions as compared to the time for -butyl acetate. The rates are dependent on the standard conditions selected (6). Most tables of relative evaporation rates are said to be at 25°C. This, however, means that the air temperature was 25°C, not that the temperature of the evaporating solvent was 25°C. As solvents evaporate, temperature drops and the drop in temperature is greatest for solvents that evaporate most rapidly. 

What is the most meaningful way to express the controllable or independent variables For example, should current density and time be taken as the experimental variables, or are time and the product of current density and time the real variables affecting response Judicious selection of the independent variables often reduces or eliminates interactions between variables, thereby leading to a simpler experiment and analysis. Also inter-relationships among variables need be recognized. For example, in an atomic absorption analysis, there are four possible variables air-flow rate, fuel-flow rate, gas-flow rate, and air/fuel ratio, but there are really only two independent variables. 

During each of the operations record all periinent information such as vacuum level, temperature, time required for the cake to crack, filtrate foaming characteristics, air flow rate during the drying periods, etc. 

Trost air mills from Colt Industries are available in five sizes. The smallest mill (Gem T) is a research unit and can be used for fine-grinding studies. Capacities of 1 to 2300 kg/h (2 to 5000 Ib/h) are available. Air-flow rates vary from 0.2 to 28 mVmin (6.5 to 1000 ftVmin). 

Grit Chambers Industries with sand or hard, inert particles in their wastewaters have found aerated grit chambers useful for the rapid separation of these inert particles. Aerated grit chambers are relatively small, with total volume based on 3-min retention at maximum flow. Diffused air is normally used to create the mixing pattern shown in Fig. 25-44, with the heavy, inert particles removed by centrifugal action and friction against the tank walls. The air flow rate is adjusted for the specific particles to be removed. Floatable solids are removed in the aerated grit chamber. It is important to provide for... 

G = air flow rate, mass/time L = waste flow rate, volume/time X = concentration of pollutant in waste, massA ohime H = Henry s constant for the pollutant in water, volume/mass... 

Off-Design Performance—This is an important eonsideration for waste heat reeovery boilers. Gas turbine performanee is affeeted by load, ambient eonditions, and gas turbine health (fouling, ete.). This ean affeet the exhaust gas temperature and the air flow rate. Adequate eonsiderations must be given to bow steam flows (low pressure and high pressure) and superheat temperatures vary with ehanges in the gas turbine operation. 

Gas turbine eompressor inlet bell-mouth pressure differential versus air flow rate... 

In our fourth step, we determine the amount of oxygen needed and the air-flow rate. To determine this, we must note the following stoichiometric reaction taking place in the furnace ... 

Air Flow - The capacity of a multijet flare to induce air flow must be calculated, to make sure that it is adequate to meet the maximum air flow requirement for smokeless combustion. (W, of Equation 4 below must be > W, of Equation 5). The term air flow capacity refers to the primary air flow rate which will be induced around each jet, and may be estimated from the following equation ... 

The primary air flow rate per jet necessary for smokeless combustion depends on the molecular weight and degree of unsaturation of the flare gas. Experience indicates that it varies linearly with percent unsaturates, from a minimum of 20 % excess air for a flare gas containing 0 % unsaturates to 35 % excess air for a gas containing 67 mol % unsaturates. Based on this relationship and a gas flow rate of 72.2 mVh per jet, the required primary air flow rate can be computed directly from the gas composition, or approximated conservatively from the following equation ... 

Reduction in energy consumption as a result of improved usage patterns and reduced air flow rates... 

Use systems that allow maximum flexibility in air flow rates and control strategies when selection of systems is based on inaccurate (preliminary) data on production processes, volumes, and raw materials to be used in the building. Emission rates from these processes and total loads might he changed during the detailed design step. 

Holmes, M. J., and C. Caygiil. 1973. Air Movement in Rooms with Low Supply Air Flow Rates. Heating and Ventilating Research Association Laboratory Report No. 83. Bracknell, UK. 

Total gate protection occurs when the air flow rate exiting the building through the gate, equals the air flow rate, G, supplied through the air curtain slot ... 

FIGURE 8.1 Model of a central recirculating system used for calculating the connection between contaminant concentrations, airflow rates, contaminant source strength, q, and air cleaner efficiency, rj. Cj p is the concentration in the supply (outside) air, c is the concentration in the room, c is the concentration in the returned air, (JaMot the total flow rate through the room, ic is the ratio between recirculated airflow rate and total air flow rate, T is the time constant for the room, and V is the room volume. 

A. Svensson. Methods for Measurement of Air Flow Rates in Ventilation Systems. Nariojiid... 

After seeding the nutrient medium with the preformed inoculum previously described, the mixture was subjected to agitation and aeration under aseptic conditions for 72 hours at 27°C to 28°C for the first 24 hours, then at 25°C to 26°C for the next 48 hours during this period, the pH was in the range of 6.4 to 6.8. Aeration was accomplished by cultivation under submerged conditions at an air flow rate of one volume of air per volume of medium per minute. After termination of the process, the mycelium was removed by filtration and the filtered broth found to contain 450 7of oleandomycin per ml of solution. 

The thesis of Steward indicates that the overall liquid film and mass transfer coefficients were functions of the gas flow rate and the column pressure and are independent of the liquid flow rate and inlet air temperature. The gas film heat transfer coefficient was found to be a function only of the air flow rate. 

Fig. 2.1. Reduction of carbohydrate in an aeration tank at various air flow rates.

Fig. 2.2. COD, cell dry weight (CDW), carbohydrate and dissolved oxygen concentrations in a 15 litres aeration tank at an air flow rate of 5 litres/min.

Air flow rate, ml/min DO, mg/1 Optical density, absorbance, A520nm Cell dry weight, mg/ml Protein concentration, mg/1 Sugar concentration, g/1... 

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